Which are examples of measurement units used for simple weather forecast

C. Degrees Centigrade

D. Percentage of relative humidity

Explanation:

These are the two most common measurements (among the list of possible answers) to talk about weather  and weather forecast.

These two cover the basic needs of weather prediction and warning for people.  The degrees are given for sure, since that directly influences how you should dress to go out. Relative humidity is also given because when temperature is high, the humidity modifies the perception of the warmth.

You'll never hear the TV weather person talk about Roentgens or centimeters of mercury.